Letter

Nature 457, 1112-1115 (26 February 2009) | doi:10.1038/nature07711; Received 3 June 2008; Accepted 8 December 2008

Large positive magnetoresistive effect in silicon induced by the space-charge effect

Michael P. Delmo1, Shinpei Yamamoto2, Shinya Kasai1, Teruo Ono1 & Kensuke Kobayashi1

  1. Institute for Chemical Research,
  2. Institute for Integrated Cell-Material Sciences, Kyoto University, Uji 611-0011, Japan

Correspondence to: Kensuke Kobayashi1 Correspondence and requests for materials should be addressed to K.K. (Email: kensuke@scl.kyoto-u.ac.jp).

Recent discoveries of large magnetoresistance in non-magnetic semiconductors1, 2, 3, 4, 5, 6, 7, 8 have gained much attention because the size of the effect is comparable to, or even larger than, that of magnetoresistance in magnetic systems9, 10, 11, 12, 13, 14. Conventional magnetoresistance in doped semiconductors is straightforwardly explained as the effect of the Lorentz force on the carrier motion15, but the reported unusually large effects imply that the underlying mechanisms have not yet been fully explored. Here we report that a simple device, based on a lightly doped silicon substrate between two metallic contacts, shows a large positive magnetoresistance of more than 1,000 per cent at room temperature (300 K) and 10,000 per cent at 25 K, for magnetic fields between 0 and 3 T. A high electric field is applied to the device, so that conduction is space-charge limited16, 17, 18. For substrates with a charge carrier density below approx1013 cm-3, the magnetoresistance exhibits a linear dependence on the magnetic field between 3 and 9 T. We propose that the observed large magnetoresistance can be explained by quasi-neutrality breaking of the space-charge effect, where insufficient charge is present to compensate the electrons injected into the device. This introduces an electric field inhomogeneity, analogous to the situation in other semiconductors in which a large, non-saturating magnetoresistance was observed1, 2, 3, 4, 5, 19. In this regime, the motions of electrons become correlated, and thus become dependent on magnetic field. Although large positive magnetoresistance at room temperature has been achieved in metal–semiconductor hybrid devices6, 7, 8, we have now realized it in a simpler structure and in a way different from other known magnetoresistive effects9, 10, 11, 12, 13, 14, 20. It could be used to develop new magnetic devices from silicon, which may further advance silicon technology.

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